What can you keep on an R-454B swap?

Since the switch to A2L refrigerants the honest answer is: it depends on three separate things, and your manufacturer has already published the rule for each of them. This site finds that rule, quotes it, and dates it.

The three questions on your quote

• Can my indoor coil stay? Usually not — but which document says so, and does your brand publish an exception?
• Can my copper line set be reused? Usually yes, with conditions. The conditions are the part that costs money when they are skipped.
• Does my furnace need a mitigation kit? One brand answers this directly. Most have not answered it at all.

Start from a model number

• The unit I already own 29 R-410A models, what replaces each one, and whether a like-for-like R-410A replacement is still an option.
• The unit I was quoted 23 R-454B models, each with what it replaces and what you can keep when you fit it.

Frequently looked up

• What replaced the Carrier 24ABB3? Replaced by the 26SCA4 on R-454B.
• What replaced the Carrier 24SCA4? Replaced by the 26SCA4 on R-454B.
• What replaced the Carrier 24SCA5? Replaced by the 26SCA5 on R-454B.
• What replaced the Carrier 24SPA6? Replaced by the 26SPA6 on R-454B.
• What replaced the Carrier 25HCE4? Replaced by the 27SCA5 on R-454B.
• What replaced the Carrier 25SCA5? Replaced by the 27SCA5 on R-454B.

Start from your brand

• American Standard Your existing R-410A coil cannot stay. American Standard states it directly: an R-410A evaporator coil cannot be used or converted with R-454B, and the R-454B coil has to be factory equipped with a mitigation control board.
• Carrier Your existing R-410A indoor coil cannot stay. Carrier states that full furnace coils are not interchangeable and that the refrigerant the indoor coil is designed for must match the outdoor unit's.

The maintained tables

• Which indoor units ship with leak detection Every coil on the site, whether detection is factory-installed, and where the manufacturer has published nothing.

Understanding the transition

• Can a Line Set Be Too Big for R-454B? Everyone worries their copper is a size small. Both manufacturers read here publish the opposite worry, and one calls it a compressor risk.
• Can You Replace Just the Outdoor AC Unit? Three questions hide inside this one: what federal law allows, what some states define it as instead, and what the manufacturer will approve.
• Do You Need a New Furnace With R-454B? One brand answers this directly and most have not answered it at all. What Carrier says about your existing gas furnace, and what a blank means.
• How Far the Line Set Can Run, and When the Answer Is No Seven Carrier variable-speed families, one tier, three different limits — and on two of them a run past a hundred feet is not permitted at all.
• How to Read the Model Number on Your Outdoor Unit The label is not one number. It carries the capacity, a variation letter that can change your line size, and a region code. How to read each one.
• Mismatched Coil and Condenser: What Is Actually Known The internet is full of confident numbers about mismatched systems. Here is the documented part: the manufacturer's rule and the certified combination.
• R-410A Coil With an R-454B Condenser: What Actually Happens The pairing people are quoted and then talked out of. What the manufacturer says about it, and what a coil that is not interchangeable actually means.
• R-454B vs R-410A: What Actually Changed What R-454B is made of, why the equipment changed rather than the refrigerant being poured into old systems, and which of the differences reach a homeowner.
• The Efficiency Number on Your Quote Belongs to a Pair No manufacturer publishes one efficiency figure for an outdoor unit. They publish a range that depends on the indoor unit it is matched with.
• The Fitting at Your Unit Is Not Your Line Size Manufacturers publish two numbers for the same copper: the connection at the service valve, and the tube the unit is rated on. They often disagree.
• The Liquid Line, Not the Big One, Sets Your Maximum Run Carrier indexes maximum line length on the thin liquid line and on which unit sits higher. On a five ton, sixty feet of drop is the end of the table.
• The R-410A Phase-Out, for People Who Just Own an Air Conditioner Which deadlines are real, which one was lifted, what you can still buy, and what none of it changes about your existing system. Six rules, each dated.
• The States Where Swapping the Condenser Is Not Servicing Eleven state rules read. Three define a new outdoor unit on an old coil as new equipment; eight write one sentence that keeps their rule off a house.
• What a Line Set One Size Too Small Actually Costs You Carrier answers this as a percentage, not a yes or no: its product data prints the cooling capacity you lose on each acceptable vapor line.
• What the EPA's 2026 Rule Changed, and What It Did Not The installation deadline for R-410A equipment was lifted in May 2026. That changes what an installer may fit, not what a manufacturer approves.
• Your New Unit Is a Heat Pump. The Vapor Line Rules Changed. Carrier's heat pump sheets accept four fewer vapor diameters than its air conditioners, and every one they withdraw is the largest the AC allows.
• Your Quote Says Long Line Application. Here Is What That Adds. Carrier's R-454B guideline lists the parts a long run requires: a solenoid, a trap, a hard start kit, a TXV — and on a heat pump, a different piston.

This is a starting point, not an approval. Everything here is read from published manufacturer documents and dated, but only the licensed contractor who signs your installation can approve a specific system for your home and your local code. Take the citations on this page to them and ask.